Do you still have the whole data folder and the config file? Then you could try to decrypt the files outside of Nextcloud with the following standalone script: https://github.com/syseleven/nextcloud-tools/blob/master/rescue/decrypt-all-files.php
Do you still have the whole data folder and the config file? Then you could try to decrypt the files outside of Nextcloud with the following standalone script: https://github.com/syseleven/nextcloud-tools/blob/master/rescue/decrypt-all-files.php